LAN Advanced Functions  2-3 
Hitachi Compute Blade 500 Series LAN Advanced Function Manual (for Intel) 
Adapter Fault Tolerance 
The AFT function provides the fault tolerance for LAN devices between the system 
equipment and the network. The function makes one team with using two LAN 
devices, one for active connection (Primary LAN device) and the other for backup 
(Secondary LAN device). 
The AFT function transmits and receives a probing packet (Broadcast Packet 
compliant with the IntelĀ® proprietary specification) as heartbeat between Primary 
LAN device and Secondary LAN device. The AFT function monitors the link state 
between the Primary LAN device and the switching HUB for active connection and the 
transmission and reception state of the probing packet between LAN devices. Even if 
the link for the Primary LAN device is disconnected to disable transmission or receive 
of the probing packet, the AFT function failover all the traffic (including the MAC 
address and the IP address) to the link for the Secondary. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Probing packet is enabled by default for the use of the AFT function. If it is 
impossible to normally transmit or receive Probing packet in heavy traffic 
network, it might repeat to failover and failback between Primary LAN device and 
Secondary LAN device. In such a case, disable the probing packet. See "How to 
Disable Monitoring Packet (AFT/ALB)". 
When using the AFT function, connect the two LAN devices to the same switching 
HUB. 
When the AFT function is used, LAN device priorities (Primary and Secondary) 
are not defined by default. See How to set LAN device priorities, for details. 
Primary LAN device 
 
Secondary LAN device